Although there are proprietary tools like MATLAB available to perform much of the computational tasks involved in Digital Image Processing, these licenses are exorbitantly costly and more importantly the software tools like MATLAB are of closed source in nature. This implies that, if you as a user would want to understand how a module or a library is implemented you don't have an option to do so! Further, in instances where one would want to append modules or functionalities to existing modules, there again the user does not have the freedom to do so.
Bearing all of this in mind, here are suggestions of computational tools which allow you to use, share, modify and redistribute the changes to the software you work with.
GNU Octave:GNU Octave is a high-level interpreted language, primarily intended for numerical computations. It provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments. It also provides extensive graphics capabilities for data visualization and manipulation. Octave is normally used through its interactive command line interface, but it can also be used to write non-interactive programs. The Octave language is quite similar to Matlab so that most programs are easily portable.
Scilab:Scilab is the free software for numerical computation providing a powerful computing environment for engineering and scientific applications.Gathering both industrial needs and scientific advances, Scilab covers a wide spectrum of areas.
matplotlib:matplotlib is a python 2D plotting library which produces publication quality figures in a variety of hardcopy formats and interactive environments across platforms. matplotlib can be used in python scripts, the python and ipython shell (ala MATLAB®* or Mathematica®†), web application servers, and six graphical user interface toolkits.
Mayavi:A tool for easy and interactive visualization of data, with seamless integration with Python scientific libraries.
SAGE: Sage is a free open-source mathematics software system licensed under the GPL. It combines the power of many existing open-source packages into a common Python-based interface, with a mission of creating a viable free open source alternative to Magma, Maple, Mathematica and Matlab.
Bearing all of this in mind, here are suggestions of computational tools which allow you to use, share, modify and redistribute the changes to the software you work with.